Daniel J. Mitchell, quoting a Cato Institute study.
Nothing deters a criminal like the threat of armed citizens. More data on this:
Professors James D. Wright and Peter Rossi surveyed 2,000 felons incarcerated in state prisons across the United States. Wright and Rossi reported that … 57% agreed with the statement, “Most criminals are more worried about meeting an armed victim than they are about running into the police.” [source]
Ever notice how often these mass killings take place in gun-free zones? It’s not just that people are “easy prey”, it’s that there is not even an implied deterrent.